This invention relates to a scroll compressor having a dampening bushing for mounting the non-orbiting scroll to reduce operational noise.
Scroll type compressors are becoming a popular refrigerant compressor. A scroll compressor includes two scroll members, each having a base and a generally spiral wrap extending from the base. The wraps interfit with each wrap being in contact with the opposed base. A non-orbiting scroll is prevented from orbiting relative to the crankcase housing. An orbiting or driven scroll is attached to a motor for orbital movement relative to the non-orbiting scroll. The scroll compressor operates by taking in low pressure fluid at a port near an outer circumference of the mutually engaged scrolls. The engaged scrolls mesh to form compression chambers in which the refrigerant fluid is contained. The chambers are progressively moved toward a discharge port positioned at a central point of the scrolls. The sealed chambers are progressively decreased in volume during movement toward the central discharge port. The decrease in the volume compresses the refrigerant fluid.
One major design challenge for a scroll compressor is maintaining the sealed chambers between the scrolls. A seal between each scroll wrap and the base of the opposite scroll and a seal between the two engaged scroll wraps must be made to create the sealed chambers. However, the refrigerant trapped in the sealed chambers creates a separating force tending to move the two scrolls away from each other. Scroll compressor designers have tapped a portion of the compressed refrigerant to a chamber in the back pressure chamber urges the scrolls into contact by causing the one scroll to move a small axial distance towards the other scroll. In one type of scroll compressor, the non-orbiting scroll moves axially relative to the driven scroll.
Typically, an axially movable non-orbiting scroll is mounted by a plurality of pins extended through bushings arranged about the circumference of the non-orbiting scroll and threaded into corresponding threaded holes in a crankcase housing. The pins and bushing guide and limit the magnitude of axial movement of the non-orbiting scroll. The pins do create a unique problem. The bushing is typically clamped by the pin. There is typically a slip fit between an opening in the fixed scroll and the bushing to allow for the axial movement. The non-orbiting scroll is typically held against the orbiting scroll once the compressor has started, thus there is little axial movement. However, there may be sometimes be xe2x80x9cchatterxe2x80x9d between the non-orbiting scroll and the bushing as the non-orbiting scroll may be biased radially outwardly and inwardly, and noise is created as the non-orbiting scroll comes into contact with the bushing. This radial movement can be caused due to a radially outward force from the entrapped refrigerant.
Therefore, to achieve low noise it is desirable to develop an apparatus for reducing the noise transmitted by an axially moving non-orbiting scroll.
A low noise scroll compressor cushions a mount between a non-orbiting scroll and a crankcase. The compressor includes the crankcase housing, an orbiting scroll supported for rotation about an axis in the crankcase, and a non-orbiting scroll mounted to the crankcase housing. The non-orbiting scroll is mounted to the crankcase housing to be movable axially relative to the driven scroll. The non-orbiting scroll mount uses at least one opening for a guide pin and bushing having a first end and a second end. The guide pin second end preferably includes a head. The guide pin head abuts the top of the bushing, and sandwiches and captures the bushing. Often a stop washer is positioned between the head and the bushing. A dampening material is positioned between an outer peripheral surface of the bushing and an inner peripheral surface of the opening in the non-orbiting scroll. The dampening bushing may be secured to the non-orbiting scroll, or it may be secured to the bushing. Now, with this invention, when the non-orbiting scroll moves, the dampening bushing reduces, or prevents the transmission of noise between the non-orbiting scroll and the bushing.
In other embodiments, the guide bushing and the dampening bushing are combined such that a dampening material is utilized to provide a single bushing providing both functions. In another embodiment, a dampening material is placed between an outer periphery of the non-orbiting scroll and an inner periphery of a housing, such a crankcase. Again, a dampening material is placed between the scroll and the housing.